Refrigeration cycle apparatus

ABSTRACT

A refrigeration cycle apparatus  100  according to the present invention includes: a refrigerant circuit  160  including a compressor  101,  a condenser ( 102  or  106 ), a first throttling device ( 103  or  105 ), a gas-liquid separator  104,  a second throttling device ( 105  or 103), and an evaporator ( 106  or  102 ); an injection passage  170  through which a gas phase refrigerant separated out in the gas-liquid separator  104  is supplied to the compressor  101  during a compression process; a detector  130  for detecting a temperature or a pressure of a refrigerant present on a downstream side of the first throttling device and on an upstream side of the second throttling device in the refrigerant circuit  160  or present in the injection passage 170; and a controller  108  for decreasing an opening degree of the first throttling device when the controller  108  recognizes, by the detector  130,  that a pressure of the refrigerant flowing into the gas-liquid separator  104  exceeds a specified pressure lower than a saturation vapor pressure, in a starting operation, a defrosting operation or a stopping operation.

TECHNICAL FIELD

The present invention relates to a refrigeration cycle apparatus in which a refrigerant is injected into a compressor during a compression process.

BACKGROUND ART

Conventionally, refrigeration cycle apparatuses in which a refrigerant is injected into a compressor during a compression process have been known. The heating capacity can be increased in such refrigeration cycle apparatuses.

For example, Patent Literature 1 discloses a refrigeration cycle apparatus 850 as shown in FIG. 22. In the refrigeration cycle apparatus 850, a gas phase refrigerant separated out in a gas-liquid separator 855 is injected into an injection cylinder 851a of a compressor 851 through an injection passage 859. The injection passage 859 is provided with an injection throttling device 860. An injection performed through the injection passage 859 increases the heating capacity at a condenser 852.

Patent Literature 2 discloses a refrigeration cycle apparatus 900 as shown in FIG. 23, which is similar to the refrigeration cycle apparatus 850 in Patent Literature 1. In the refrigeration cycle apparatus 900, carbon dioxide is used as the refrigerant, and an injection passage 902 through which the refrigerant is injected into a compressor 901 is provided with no throttling device.

CITATION LIST Patent Literature

PTL 1JP 61(1986)-197960 A

PTL 2JP 11(1999)-173687 A

SUMMARY OF INVENTION Technical Problem

Ideally, a gas phase refrigerant and a liquid phase refrigerant are separated from each other completely in a gas-liquid separator. However, in a transition period such as a starting operation, the gas phase refrigerant and the liquid phase refrigerant are not separated completely from each other in the gas-liquid separator and the liquid phase refrigerant is mixed into the gas phase refrigerant in some cases. Such a phenomenon occurs more prominently when the pressure in the gas-liquid separator is closer to a saturation vapor pressure. Thus, there is a possibility of the liquid phase refrigerant being injected into a compressor through an injection passage together with the gas phase refrigerant. When such an injection of the liquid phase refrigerant into the compressor occurs excessively, a problem of liquid compression arises in the compressor.

To deal with this, it is conceivable to close the throttling device 860 provided to the injection passage 859 in the starting operation as disclosed in Patent Literature 1. In this case, however, the effect of increasing the heating capacity by injection cannot be obtained in the starting operation.

The phenomenon in which the liquid phase refrigerant is mixed into the gas phase refrigerant as described above occurs also in a defrosting operation and a stopping operation in the same manner.

The phenomenon as described above hardly is a problem for the refrigeration cycle apparatus 900 disclosed in Patent Literature 2 because carbon dioxide, which reaches a supercritical state on a high pressure side, is used as the refrigerant. That is, Patent Literature 2 neither discloses nor suggests a technical idea of preventing the liquid phase refrigerant from being injected into the compressor through the injection passage.

In view of the foregoing, the present invention is intended to provide a refrigeration cycle apparatus capable of suppressing the liquid compression without shutting an injection passage even in the case of using a refrigerant that does not reach the supercritical state on a high pressure side.

Solution to Problem

In order to solve the above-mentioned problem, the present invention provides a refrigeration cycle apparatus comprising: a refrigerant circuit including a compressor for compressing a refrigerant, a condenser for condensing the refrigerant compressed in the compressor, a first throttling device for expanding the refrigerant condensed in the condenser, a gas-liquid separator for separating the refrigerant expanded in the first throttling device into a gas phase refrigerant and a liquid phase refrigerant, a second throttling device for expanding the liquid phase refrigerant separated out in the gas-liquid separator, and an evaporator for evaporating the refrigerant expanded in the second throttling device, the refrigerant circuit being a refrigerant circuit through which the refrigerant that does not reach a supercritical state after being compressed in the compressor circulates; an injection passage through which the gas phase refrigerant separated out in the gas-liquid separator is supplied to the compressor during a compression process; a detector for detecting a temperature or a pressure of the refrigerant present on a downstream side of the first throttling device and on an upstream side of the second throttling device in the refrigerant circuit or present in the injection passage; and a controller for decreasing an opening degree of the first throttling device when the controller recognizes, by the detector, that a pressure of the refrigerant flowing into the gas-liquid separator exceeds a specified pressure lower than a saturation vapor pressure, in a starting operation, a defrosting operation or a stopping operation.

Advantageous Effects of Invention

In the refrigeration cycle apparatus according to the present invention, the opening degree of the first throttling device is adjusted so that the pressure of the refrigerant flowing into the gas-liquid separator is equal to or lower than a specified pressure lower than a saturation vapor pressure, and thereby the amount of the liquid phase refrigerant injected into the compressor can be suppressed to an extent where the liquid compression is not a problem. This makes it possible to suppress the liquid compression in the starting operation, the defrosting operation or the stopping operation without shutting the injection passage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a Mollier diagram of the refrigeration cycle according to Embodiment 1 of the present invention.

FIG. 3 is a flow chart illustrating a controlling method in Embodiment 1 of the present invention.

FIG. 4 is a Mollier diagram for explaining the effect of the control in Embodiment 1 of the present invention.

FIG. 5 is a graph for explaining a relationship between the pressure of a refrigerant flowing into a gas-liquid separator and the flow rate of a gas phase refrigerant injected into a compressor.

FIG. 6 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 2 of the present invention.

FIG. 7 is a flow chart illustrating a controlling method in Embodiment 2 of the present invention.

FIG. 8 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 3 of the present invention.

FIG. 9 is a flow chart illustrating a controlling method in Embodiment 3 of the present invention.

FIG. 10 is a flow chart illustrating a controlling method in another embodiment of the present invention.

FIG. 11 is a flow chart illustrating a controlling method in another embodiment of the present invention.

FIG. 12 is a configuration diagram of the refrigeration cycle apparatus for explaining a first normal operation.

FIG. 13 is a Mollier diagram of the refrigeration cycle in the first normal operation.

FIG. 14 is a flow chart illustrating a controlling method in the first normal operation.

FIG. 15 is a Mollier diagram for explaining the effect of the control in the first normal operation.

FIG. 16 is a configuration diagram of the refrigeration cycle apparatus for explaining a second normal operation.

FIG. 17 is a flow chart illustrating a controlling method in the second normal operation.

FIG. 18 is a configuration diagram of the refrigeration cycle apparatus for explaining a third normal operation.

FIG. 19 is a flow chart illustrating a controlling method in the third normal operation.

FIG. 20 is a configuration diagram of the refrigeration cycle apparatus for explaining a fourth normal operation.

FIG. 21 is a flow chart illustrating a controlling method in the fourth normal operation.

FIG. 22 is a configuration diagram of a conventional refrigeration cycle apparatus.

FIG. 23 is a configuration diagram of a conventional refrigeration cycle apparatus.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments for carrying out the present invention are described with reference to the drawings.

Embodiment 1

The configuration of a refrigeration cycle apparatus 100 according to Embodiment 1 of the present invention is described with reference to FIG. 1. Although the refrigeration cycle apparatus 100 configured as an air conditioner is described in the present embodiment, the refrigeration cycle apparatus according to the present invention is applicable to a water heater, etc. FIG. 1 shows a configuration for suppressing the liquid compression in a starting operation. As shown in FIG. 1, the refrigeration cycle apparatus 100 of the present embodiment includes a refrigerant circuit 160 through which a refrigerant circulates, and an injection passage 170.

The refrigerant circuit 160 is a circuit through which the refrigerant circulates. The refrigerant circuit 160 includes a compressor 101, an indoor heat exchanger 102, an indoor side throttling device 103, a gas-liquid separator 104, an outdoor side throttling device 105, an outdoor heat exchanger 106, and a four-way valve 120 (corresponding to the switching device in Claims). The four-way valve 120 serves to switch between a heating operation and a cooling operation. A first port of the four-way valve 120 is connected to a discharge port of the compressor 101 with a pipe. A fourth port of the four-way valve 120 is connected to a suction port of the compressor 101 with a pipe. A second port of the four-way valve 120 is connected to a third port with a pipe via the indoor heat exchanger 102, the indoor side throttling device 103, the gas-liquid separator 104, the outdoor side throttling device 105, and the outdoor heat exchanger 106.

The injection passage 170 is a passage through which a gas phase refrigerant separated out by the gas-liquid separator 104 is supplied to the compressor 101 during a compression process. The injection passage 170 is provided with a temperature sensor 130 (corresponding to the detector in Claims) for detecting the temperature of the refrigerant flowing through the injection passage 170.

In the present embodiment, a refrigerant that does not reach a supercritical state after being compressed by the compressor 101 is used as the refrigerant. Examples of such a refrigerant include a fluorocarbon refrigerant.

The refrigeration cycle apparatus 100 further includes a controller 108. The controller 108 controls mainly the rotation speed of the compressor 101, the opening degree of the indoor side throttling device 103 and the opening degree of the outdoor side throttling device 105, and the four-way valve 120. The refrigeration cycle apparatus 100 in the present embodiment is characterized by that the controller 108 controls the opening degree of the indoor side throttling device 103 and the opening degree of the outdoor side throttling device 105 based on values detected by the temperature sensor 130. The control is described later in detail.

Next, the flow of the refrigerant in the refrigerant circuit 160 is described. In the heating operation, the four-way valve 120 is switched to a state that allows the refrigerant to flow in the direction indicated by the solid line in FIG. 1. In the cooling operation, the four-way valve 120 is switched to a state that allows the refrigerant to flow in the direction indicated by the dashed line in FIG. 1.

In the heating operation, the refrigerant compressed by the compressor 101 is condensed in the indoor heat exchanger 102. The refrigerant condensed in the indoor heat exchanger 102 is expanded in the indoor side throttling device 103. The refrigerant expanded in the indoor side throttling device 103 is separated into a gas phase refrigerant and a liquid phase refrigerant in the gas-liquid separator 104. The liquid phase refrigerant separated out in the gas-liquid separator 104 is expanded in the outdoor side throttling device 105. The refrigerant expanded in the outdoor side throttling device 105 is evaporated in the outdoor heat exchanger 106. The refrigerant that has evaporated in the outdoor heat exchanger 106 is drawn into the compressor 101. In this case, the indoor heat exchanger 102 serves as a condenser and the outdoor heat exchanger 106 serves as an evaporator.

In the cooling operation, the refrigerant circulates through the compressor 101, the outdoor heat exchanger 106, the outdoor side throttling device 105, the gas-liquid separator 104, the indoor side throttling device 103 and the indoor heat exchanger 102 in this order. In this case, the indoor heat exchanger 102 serves as an evaporator and the outdoor heat exchanger 106 serves as a condenser.

Next, the state of the refrigerant flowing through the refrigerant circuit 160 and the injection passage 170 is described with reference to the Mollier diagram in FIG. 2. In the description below, the indoor heat exchanger 102 in the heating operation or the outdoor heat exchanger 106 in the cooling operation is referred to as a condenser, and the indoor heat exchanger 102 in the cooling operation or the outdoor heat exchanger 106 in the heating operation is referred to as an evaporator. Also, in the description, the indoor side throttling device 103 in the heating operation or the outdoor side throttling device 105 in the cooling operation (that is, the throttling device on the upstream side of the gas-liquid separator 104) is referred to as a first throttling device, and the indoor side throttling device 103 in the cooling operation or the outdoor side throttling device 105 in the heating operation (that is, the throttling device on the downstream side of the gas-liquid separator 104) is referred to as a second throttling device. This is also the case with Embodiments 2, 3 and Other Embodiments to be described later.

The low pressure refrigerant (State A) drawn into the compressor 101 is compressed to have an intermediate pressure (State B) and merged into the refrigerant supplied from the injection passage 170 (State C), and then compressed further to have a high temperature and a high pressure (State D). The high temperature, high pressure refrigerant discharged from the compressor 101 flows into the condenser and is cooled and condensed therein (State E). The high pressure refrigerant flowed out of the condenser is expanded by the first throttling device to have an intermediate pressure (State F). This refrigerant is separated into a refrigerant (State I) containing a gas phase refrigerant as a main component and a liquid phase refrigerant (State G) in the gas-liquid separator 104. The refrigerant containing the gas phase refrigerant as a main component flows into the injection passage 170. The liquid phase refrigerant flows into the second throttling device. The liquid phase refrigerant that has flowed into the second throttling device is expanded further and turns into a low pressure refrigerant (State H). Thereafter, the low pressure refrigerant is evaporated in the evaporator to be gaseous (State A), and then passes through the four-way valve 120 and is drawn into the compressor 101 again. The refrigerant containing the gas phase refrigerant as a main component separated in the gas-liquid separator 104 passes through the injection passage 170 and is drawn into the compressor 101 during the compression process.

Ideally, the refrigerant separated in the gas-liquid separator 104 and flowing into the injection passage 170 contains no liquid phase component (that is, the refrigerant is in State J in FIG. 2). However, the vapor phase component and the liquid phase component cannot be separated completely from each other in some cases. That is, State I may move to the left side of the saturation vapor line in FIG. 2. In a starting operation as in the present embodiment, this problem occurs prominently.

Mixing of the liquid phase refrigerant into the gas phase refrigerant in the gas-liquid separator 104 occurs more prominently when the pressure, referred to as State F in FIG. 2, of the refrigerant flowing into the gas-liquid separator 104 is closer to a saturation vapor pressure. Thus, in order to suppress the amount of the liquid phase component in the refrigerant containing the gas phase refrigerant as a main component separated in the gas-liquid separator 104, it is effective to keep the pressure in State F in FIG. 2 equal to or lower than a specified pressure (1.25 MPa, for example (when the refrigerant is R410A)) that is lower the saturation vapor pressure (pressure at the intersection between the line segment EF and the saturation liquid line in FIG. 2). This increases the amount of the vapor phase component and decreases the liquid phase component in the refrigerant (State I) flowing through the injection passage 170 (State I moves rightward in FIG. 2). Thereby, the liquid compression in the compressor 101 is suppressed.

In the present embodiment, the controller 108 decreases the opening degree of the first throttling device and increases the opening degree of the second throttling device when the controller 108 recognizes, by the temperature sensor 130, that the pressure of the refrigerant flowing into the gas-liquid separator 104 exceeds the specified pressure in the starting operation. Hereinafter, the control in the present embodiment is described with reference to the flow chart in FIG. 3. This control may be performed while the output of the compressor 101 is kept constant, or may be performed while the output of the compressor 101 is being changed. Moreover, the control may be performed concurrently with the control of another device.

The controller 108 set the opening degree of the first throttling device and the opening degree of the second throttling device to specified opening degrees, and then starts running the refrigeration cycle apparatus to perform the starting operation.

First, the controller 108 determines the large/small relationship between a time T that has elapsed from the start of the operation and a threshold value T1 (5 minutes, for example) (Step S201). If the relationship of T>T1 holds (YES in Step S201), the sequence proceeds to Step S202 and the controller 108 ends the starting operation. If the relationship of T>T1 does not hold (NO in Step S201), the sequence proceeds to Step S211 and the controller 108 continues the starting operation. The time T that has elapsed from the start of the operation can be measured by a timer 109 provided to the controller 108.

In Step S202, a shifting operation is performed to set the opening degree of the first throttling device and the opening degree of the second throttling device to opening degrees suitable for a normal operation, and then the sequence proceeds to Step S203 and the controller 108 performs the normal operation.

In Step S211, the temperature sensor 130 detects a temperature Ti of the refrigerant flowing through the injection passage 170.

Subsequently, the controller 108 determines the large/small relationship between the temperature Ti and a threshold value Ti1 defined in advance (10° C., for example) (Step S212). In the present embodiment, if the relationship of Ti>Ti1 holds, the controller 108 determines that the pressure of the refrigerant flowing into the gas-liquid separator 104 exceeds the specified pressure lower than the saturation vapor pressure. If the relationship of Ti>Ti1 holds (YES in Step S212), the controller 108 decreases the opening degree of the first throttling device by ΔA1 and increases the opening degree of the second throttling device by ΔA2 (Step S213), and the sequence returns to Step S201. If the relationship of Ti>Ti1 does not hold (NO in Step S212), the sequence returns to Step S201. That is, the controller 108 monitors Ti in the starting operation, and if Ti is larger than Ti1, decreases gradually the opening degree of the first throttling device and increases gradually the opening degree of the second throttling device until Ti becomes equal to or smaller than Ti1.

The control in accordance with the flow chart in FIG. 3 can decrease the opening degree of the first throttling device and increase the opening degree of the second throttling device based on the temperature of the refrigerant in the injection passage 170. Thereby, the pressure of the refrigerant flowing into the gas-liquid separator 104 can be lowered.

The effect of the control in accordance with the flow chart in FIG. 3 is described with reference to the Mollier diagram in FIG. 4. Before the control in accordance with the flow chart in FIG. 3 is performed in the starting operation, the state of the refrigerant in the refrigeration cycle apparatus 100 changes in the order of A, B, C, D, E, F, G, H and A in FIG. 4. On the other hand, after the control in accordance with the flow chart in FIG. 3, the pressure of the refrigerant flowing into the gas-liquid separator 104 lowers. That is, the state of the refrigerant in the refrigeration cycle apparatus 100 changes in the order of A, B′, C′, D′, E, F′, G′, H′ and A.

As shown in FIG. 4, the refrigerant flowing into the gas-liquid separator 104 has a lower pressure in the state (State F′) after the above-mentioned control is performed than in the state (state F) before the above-mentioned control is performed. As shown in FIG. 5, in the situation presumed in the present embodiment, when the pressure of the refrigerant flowing into the gas-liquid separator 104 decreases, the flow rate of the gas phase refrigerant injected into the compressor 101 increases (an operating point moves from Point X to Point Y in FIG. 5). That is, the amount of the liquid phase component contained in the refrigerant in State F′ is smaller than that of the liquid phase component contained in the refrigerant in State F. In a transition period such as the starting operation, there occurs a phenomenon in which the gas phase refrigerant and the liquid phase refrigerant are not separated completely from each other in the gas-liquid separator 104 and the liquid phase refrigerant is more likely to be mixed into the gas phase refrigerant. However, this phenomenon is mitigated when the amount of the liquid phase refrigerant flowing into the gas-liquid separator 104 is decreased. Thus, in the present embodiment, the amount of the liquid phase component in the refrigerant injected based on Ti1 is suppressed to an allowable degree. Thereby, the liquid compression is suppressed.

In the present embodiment, the control is performed based on the temperature Ti of the refrigerant in the injection passage 170, but it can also be performed based on another value. For example, the opening degree of the first throttling device and the opening degree of the second throttling device may be controlled based on the temperature of the refrigerant between the first throttling device and the gas-liquid separator 104 or between the gas-liquid separator 104 and the second throttling device in the refrigerant circuit 160, or the temperature of the refrigerant in the gas-liquid separator 104.

It also is possible to detect, using a pressure sensor instead of the temperature sensor, the pressure of the refrigerant in the injection passage 170 or the pressure of the refrigerant present on the downstream side of the first throttling device and on the upstream side of the second throttling device in the refrigerant circuit 160 so as to control the opening degree of the first throttling device and the opening degree of the second throttling device based on this value.

In the present embodiment, both of the opening degree of the first throttling device and the opening degree of the second throttling device are controlled. This makes it possible to suppress the variation in the pressure difference between a pressure on the high pressure side and a pressure on the low pressure side in the refrigeration cycle. Moreover, by controlling both of the opening degree of the first throttling device and the opening degree of the second throttling device, it also is possible to adjust the degree of dryness of the refrigerant flowing into the compressor 101 via the evaporator to an appropriate value. Thereby, the heating capacity of the refrigeration cycle apparatus 100 can be enhanced. However, the controller 108 may only decrease gradually the opening degree of the first throttling device while keeping the opening degree of the second throttling device constant. This also can suppress the liquid compression.

The four-way valve (switching device) 120 may be omitted. This makes the configuration of the refrigeration cycle apparatus simple, and advantageous from the viewpoints of maintenance and cost. In the case where the four-way valve 120 is omitted, and the flowing direction of the refrigerant is fixed as in a refrigeration cycle apparatus constituting a water heater or the like, a fixed throttling device may be used as the second throttling device. This makes the configuration further simpler.

In the present embodiment, the injection passage 170 is provided with no injection throttling device. Thereby, an advantageous configuration is achieved from the view point of cost. However, even in the case where an injection throttling device is provided (for emergency, etc.), the above-mentioned control may be performed while the injection throttling device is kept open.

Embodiment 2

FIG. 6 shows a refrigeration cycle apparatus 200 according to Embodiment 2 of the present invention. The refrigeration cycle apparatus 200 of the present embodiment is different from the refrigeration cycle apparatus 100 of Embodiment 1 in that the refrigeration cycle apparatus 200 is provided with a temperature sensor 131 (corresponding to the condenser temperature sensor in Claims) capable of measuring the temperature of the refrigerant flowing through the indoor heat exchanger 102 that functions as the condenser in the heating operation. There is no difference other than this, and the action of the refrigeration cycle apparatus 200 of the present embodiment is the same as the action of the refrigeration cycle apparatus 100 of Embodiment 1 except for the control described below. In the refrigeration cycle apparatus 200 shown in FIG. 6, the indoor side throttling device 103 and the outdoor side throttling device 105 are controlled as described below in the heating operation. However, by providing the temperature sensor 131 to the outdoor heat exchanger 106 and exchanging roles between the indoor side throttling device 103 and the outdoor side throttling device 105, it is possible to perform the same control as in the present embodiment when the refrigeration cycle apparatus performs the cooling operation.

In the present embodiment, the controller 108 determines whether to end the starting operation or not based on a rate of change with time, ΔTc, in a temperature Tc of the refrigerant flowing through the condenser.

The control of the opening degree of the indoor side throttling device 103 (first throttling device) and the opening degree of the outdoor side throttling device 105 (second throttling device) performed by the controller 108 is described with reference to the flow chart shown in FIG. 7.

The flow chart shown in FIG. 7 is given by replacing Step S201 in the flow chart shown in FIG. 3 with Step S401 to Step S403.

First, the temperature sensor 131 detects the temperature Tc of the refrigerant flowing through the condenser in Step S401, and the sequence proceeds to Step S402. The temperature Tc is stored in the controller 108 each time.

In Step S402, the rate of change with time, ΔTc, in the temperature of the refrigerant flowing through the condenser is calculated from the detected temperature Tc, a temperature Tc′ detected one time step earlier and stored in the controller 108, and a time step Δt.

In Step S403, the large/small relationship between the calculated rate of change with time, ΔTc, and a threshold value ΔTc1 is determined. If the relationship of ΔTe<ΔTc1 holds (YES in Step S403), the sequence proceeds to Step S202. If the relationship of ΔTc<ΔTc1 does not hold (No in Step S403), the sequence proceeds to Step S211.

The control in accordance with the flow chart in FIG. 7 can determine the timing to proceed to the shifting operation (that is, the timing to end the starting operation) based on the state of the refrigerant flowing through the condenser. Thereby, the sequence can proceed to the shifting operation at a more appropriate timing in this control than in the control of Embodiment 1.

Embodiment 3

FIG. 8 shows a refrigeration cycle apparatus 300 according to Embodiment 3 of the present invention. The refrigeration cycle apparatus 300 of the present embodiment is different from the refrigeration cycle apparatus 100 of Embodiment 1 in that the refrigeration cycle apparatus 300 is provided with a temperature sensor 133 (corresponding to the evaporator temperature sensor in Claims) capable of measuring the temperature of the refrigerant flowing through the outdoor heat exchanger 106 that functions as the evaporator in the heating operation. There is no difference other than this, and the action of the refrigeration cycle apparatus 300 of the present embodiment is the same as the action of the refrigeration cycle apparatus 100 of Embodiment 1 except for the control described below. In the refrigeration cycle apparatus 300 shown in FIG. 8, the indoor side throttling device 103 and the outdoor side throttling device 105 are controlled as described below in the heating operation. However, by providing the temperature sensor 133 to the indoor heat exchanger 102 and exchanging roles between the indoor side throttling device 103 and the outdoor side throttling device 105, it is possible to perform the same control as in the present embodiment when the refrigeration cycle apparatus performs the cooling operation.

In the present embodiment, the controller 108 determines whether to end the starting operation or not based on a rate of change with time, ΔTe, in a temperature Te of the refrigerant flowing through the evaporator.

The control of the opening degree of the indoor side throttling device 103 (first throttling device) and the opening degree of the outdoor side throttling device 105 (second throttling device) performed by the controller 108 is described with reference to the flow chart shown in FIG. 9.

The flow chart shown in FIG. 9 is given by replacing Step S201 in the flow chart shown in FIG. 3 with Step S501 to Step S503.

First, the temperature sensor 133 detects the temperature Te of the refrigerant flowing through the evaporator in Step S501, and the sequence proceeds to Step S502. The temperature Te is stored in the controller 108 each time.

In Step S502, the rate of change with time, ΔTe, in the temperature of the refrigerant flowing through the condenser is calculated from the detected temperature Te, a temperature Te′ detected one time step earlier and stored in the controller 108, and the time step At.

In Step S503, the large/small relationship between the calculated rate of change with time, ΔTe, and a threshold value ΔTe1 is determined. If the relationship of ΔTe<ΔTe1 holds (YES in Step S503), the sequence proceeds to Step S202. If the relationship of ΔTe<ΔTe1 does not hold (NO in Step S503), the sequence proceeds to Step S211.

The control in accordance with the flow chart in FIG. 9 can determine the timing to proceed to the shifting operation (that is, the timing to end the starting operation) based on the state of the refrigerant flowing through the evaporator. Thereby, the sequence can proceed to the shifting operation at a more appropriate timing in this control than in the control of Embodiment 1.

Other Embodiments

Although the controls described in the above-mentioned Embodiments are provided to prevent the liquid compression in the starting operation, they are applicable to prevent the liquid compression in other operations as well.

In the defrosting operation, for example, the liquid phase refrigerant is likely to be injected into the compressor 101. Also, in the stopping operation, the drawing temperature in the compressor 101 lowers, the amount of the liquid phase component contained in the refrigerant increases, and the liquid compression is likely to occur. Also in these operations, the liquid compression can be suppressed by the same configuration as that of the refrigeration cycle apparatus 100 in FIG. 1.

FIG. 10 shows a flow chart for preventing the liquid compression in the defrosting operation.

The controller 108 starts the defrosting operation when, for example, the temperature of the outdoor heat exchanger 106 becomes equal to or lower than a specified temperature (−5° C., for example).

First, in Step S601, the controller 108 determines the large/small relationship between a time T that has elapsed from the start of the defrosting operation and a threshold value T2 (10 minutes, for example). If the relationship of T>T2 holds (YES in Step S601), the sequence proceeds to Step S602 and the controller 108 ends the defrosting operation. If the relationship of T>T2 does not hold (NO in Step S601), the sequence proceeds to Step S611 and the controller 108 continues the defrosting operation. The time T that has elapsed from the start of the operation can be measured by the timer 109 provided to the controller 108.

The controller 108 performs the shifting operation in Step S602, and then the sequence proceeds to Step S603 to perform the normal operation.

In Step S611, the temperature sensor 130 detects the temperature Ti of the refrigerant in the injection passage 170.

Subsequently, the controller 108 determines the large/small relationship between the temperature Ti and the threshold value Ti1 defined in advance (Step S612). If the relationship of Ti>Ti1 holds (YES in Step S612), the controller 108 decreases the opening degree of the first throttling device by ΔA1 and increases the opening degree of the second throttling device by ΔA2 (Step S613), and the sequence returns to Step S601. If the relationship of Ti>Ti1 does not hold (NO in Step S612), the sequence returns to Step S601.

The control in accordance with the flow chart in FIG. 10 can decrease the opening degree of the first throttling device and increase the opening degree of the second throttling device based on the temperature of the refrigerant in the injection passage 170. Thereby, the pressure of the refrigerant flowing into the gas-liquid separator 104 can be lowered in the defrosting operation. That is, it is possible to reduce the amount of the liquid phase component contained in the refrigerant passing through the injection passage 170, and thereby suppressing the liquid compression.

In the flow chart in FIG. 10, the defrosting operation is controlled to end after the specified time T2 has elapsed from the start of the defrosting operation. However, the defrosting operation may be ended when the temperature of the outdoor heat exchanger 106 exceeds a certain temperature, for example.

Next, FIG. 11 shows a flow chart for preventing the liquid compression in the stopping operation.

First, in Step S701, the controller 108 determines the large/small relationship between a time T that has elapsed from the start of the stopping operation and a threshold value T3 (3 minutes, for example). If the relationship of T>T3 holds (YES in Step S701), the sequence proceeds to Step S702 and the controller 108 ends the stopping operation. If the relationship of T>T3 does not hold (NO in Step S701), the sequence proceeds to Step S711 and the controller 108 continues the stopping operation. The time T that has elapsed from the start of the operation can be measured by the timer 109 provided to the controller 108.

In Step S711, the temperature sensor 130 detects the temperature Ti of the refrigerant in the injection passage 170.

Subsequently, the controller 108 determines the large/small relationship between the temperature Ti and the threshold value Ti1 defined in advance (Step S712). If the relationship of Ti>Ti1 holds (YES in Step S712), the controller 108 decreases the opening degree of the first throttling device by ΔA1 and increases the opening degree of the second throttling device by ΔA2 (Step S713), and the sequence returns to Step S701. If the relationship of Ti>Ti1 does not hold (NO in Step S712), the sequence returns to Step S701.

The controlling in accordance with the flow chart in FIG. 11 can decrease the opening degree of the first throttling device and increase the opening degree of the second throttling device based on the temperature of the refrigerant in the injection passage 170. Thereby, the pressure of the refrigerant flowing into the gas-liquid separator 104 can be lowered in the stopping operation. That is, it is possible to reduce the amount of the liquid phase component contained in the refrigerant passing through the injection passage 170, and thereby suppressing the liquid compression.

In each of the defrosting operation and the stopping operation, instead of performing the control based on the temperature Ti of the refrigerant in the injection passage 170, it also is possible to perform the control based on another value. For example, the opening degree of the first throttling device and the opening degree of the second throttling device may be controlled based on the temperature of the refrigerant between the first throttling device and the gas-liquid separator 104 or between the gas-liquid separator 104 and the second throttling device in the refrigerant circuit 160, or the temperature of the refrigerant in the gas-liquid separator 104. That is, the opening degree of the first throttling device and the opening degree of the second throttling device may be controlled based on the temperature of the refrigerant present on the downstream side of the first throttling device and on the upstream side of the second throttling device in the refrigerant circuit 160, or the temperature of the refrigerant in the injection passage 107.

It also is possible to detect, using a pressure sensor instead of the temperature sensor, the pressure of the refrigerant in the injection passage 170 or the pressure of the refrigerant present on the downstream side of the first throttling device and on the upstream side of the second throttling device in the refrigerant circuit 160 so as to control the opening degree of the first throttling device and the opening degree of the second throttling device based on this value.

The controller 108 may only decrease gradually the opening degree of the first throttling device while keeping the opening degree of the second throttling device constant. The four-way valve (switching device) 120 may be omitted. Also, with the four-way valve 120 being omitted, a fixed throttling device may be used as the second throttling device

(Control in Normal Operation)

When controlled as mentioned above, the refrigeration cycle apparatus can perform the starting operation, the defrosting operation and the stopping operation in which the liquid compression hardly occurs while the effect of injection is exhibited. In the normal operation, the refrigeration cycle apparatus preferably is operated as described in First Normal Operation, Second Normal Operation, Third Normal Operation, or Fourth Normal Operation below. Thereby, it is possible to suppress an abnormal increase in the pressure of the refrigerant on the high pressure side in the refrigeration cycle in the normal operation, and to achieve the effect of enhancing the heating capacity by injection while preventing the liquid refrigerant from being injected into the compressor.

(First Normal Operation)

The first normal operation is described with reference to a refrigeration cycle apparatus 150 (FIG. 12) capable of performing the first normal operation.

A fluorocarbon refrigerant is used as the refrigerant also in the refrigeration cycle apparatus 150. However, the effect of the first normal operation is exhibited even when a refrigerant, such as carbon dioxide, that reaches a supercritical state after being compressed by the compressor 101 is used as the refrigerant. Thus, the term “radiator” is used instead of the term “condenser” hereinafter.

The state of the refrigerant flowing through the refrigerant circuit 160 and the injection passage 170 in the refrigeration cycle apparatus 150 in the first normal operation are described with reference to the Mollier diagram in FIG. 13. In the description below, the indoor heat exchanger 102 in the heating operation or the outdoor heat exchanger 106 in the cooling operation is referred to as the radiator, and the indoor heat exchanger 102 in the cooling operation or the outdoor heat exchanger 106 in the heating operation is referred to as the evaporator. Also, in the description, the indoor side throttling device 103 in the heating operation or the outdoor side throttling device 105 in the cooling operation (that is, the throttling device on the upstream side of the gas-liquid separator 104) is referred to as the first throttling device, and the indoor side throttling device 103 in the cooling operation or the outdoor side throttling device 105 in the heating operation (that is, the throttling device on the downstream side of the gas-liquid separator 104) is referred to as the second throttling device. This is also the case with the second normal operation to fourth normal operation to be described later.

The low pressure refrigerant (State 0) drawn into the compressor 101 is compressed to have an intermediate pressure (State P) and merged into the refrigerant supplied from the injection passage 170 (State Q), and then compressed further to have a high temperature and a high pressure (State R). The high temperature, high pressure refrigerant discharged from the compressor 101 flows into the radiator and is cooled and radiates heat therein (state S). The high pressure refrigerant flowed out of the radiator is expanded by the first throttling device to have an intermediate pressure (State T). This refrigerant is separated into a gas phase refrigerant and a liquid phase refrigerant (State U) in the gas-liquid separator 104. The gas phase refrigerant flows into the injection passage 170. The liquid phase refrigerant flows into the second throttling device. The liquid phase refrigerant that has flowed into the second throttling device is expanded further and turns into a low pressure refrigerant (State V). Thereafter, the low pressure refrigerant is evaporated in the evaporator to be gaseous (State O), and then passes through the four-way valve 120 and is drawn into the compressor 101 again. The gas phase refrigerant separated out in the gas-liquid separator 104 passes through the injection passage 170 and is drawn into the compressor 101 during the compression process.

In the first normal operation, the controller 108 controls the rotation speed of the compressor 102 in accordance with, for example, a load required by a user, and adjusts the opening degrees of the first throttling device and the second throttling device so that the pressure of the refrigerant flowing into the gas-liquid separator 104 is equal to the specified pressure stored in advance.

In the first normal operation, the pressure (the pressure in State R and State S in FIG. 13) of the refrigerant on the high pressure side in the refrigeration cycle may be excessively high for a certain reason (for example, when the outside air temperature rises and when a blower fan of the radiator stops because of failure) in a steady operation. In such a case, the controller 108 shifts the operating state from the steady operation to a high-pressure-side abnormality eliminating operation, and the opening degrees of the first throttling device and the second throttling device are adjusted so that the pressure on the high pressure side in the refrigeration cycle is lowered and the pressure of the refrigerant (State T) flowing into the gas-liquid separator 104 is kept equal to or lower than the saturation vapor pressure (the pressure at the intersection between the line segment ST and the saturation liquid line in FIG. 13).

In the first normal operation, the controller 108 controls the opening degree of the indoor side throttling device 103 and the opening degree of the outdoor side throttling device 105 based on a value detected by the temperature sensor 131 (high pressure side detector) capable of measuring the temperature of the refrigerant in the indoor heat exchanger 102 that functions as the radiator in the heating operation. This control may be performed while the output of the compressor 101 is kept constant, or may be performed while the output of the compressor 101 is being changed. Moreover, the control may be performed concurrently with the control of another device. In the refrigeration cycle apparatus 150 shown in FIG. 12, the indoor side throttling device 103 and the outdoor side throttling device 105 are controlled as described below in the heating operation. By providing the temperature sensor 133 to the outdoor heat exchanger 106 and exchanging roles between the indoor side throttling device 103 and the outdoor side throttling device 105, it is possible to perform the same control as in the first normal operation when the refrigeration cycle apparatus performs the cooling operation.

Hereinafter, the control of the opening degree of the indoor side throttling device 103 (first throttling device) and the opening degree of the outdoor side throttling device 105 (second throttling device) performed by the controller 108 is described with reference to the flow chart shown in FIG. 14.

First, in Step S261, the temperature sensor 131 detects a temperature Th of the refrigerant flowing through the radiator.

Subsequently, the controller 108 determines the large/small relationship between the temperature Th detected in Step 261 and a threshold value Th1 (55° C., for example) defined in advance (Step S262). If the relationship of Th>Th1 holds (YES in Step S262), the sequence proceeds to Step S263 and the controller 108 shifts the operating state from the steady operation to the high-pressure-side abnormality eliminating operation. If the relationship of Th>Th1 does not hold (NO in Step S262), the sequence returns to Step S261. That is, in the first normal operation, the determination of whether to shift the operating state to the high-pressure-side abnormality eliminating operation is made according to the large/small comparison between Th and Th1. Step S261 and Step S262 are in the flow of the steady operation.

In Step S263 (main step), the controller 108 increases the opening degree of the first throttling device by ΔA3 and increases the opening degree of the second throttling device by ΔA4, and the sequence proceeds to Step S264. Here, ΔA3 and the ΔA4 are set to values that cause no increase in the pressure of the refrigerant in the gas-liquid separator 104 even if Step S263 is performed. Such ΔA3 and ΔA4 can be determined by an experiment, etc. conducted in advance.

In Step S264, the temperature sensor 131 detects once again the temperature Th of the refrigerant flowing through the radiator. In Step S265, the controller 108 determines the large/small relationship between the temperature Th detected in Step 264 and the threshold value Th1 defined in advance. If the relationship of Th>Th1 holds (YES in Step S265), the sequence returns to Step S263 and the controller 108 continues the high-pressure-side abnormality eliminating operation. If the relationship of Th>Th1 does not hold (NO in Step S265), the sequence returns to Step S261 (comes back to the steady operation) and the controller 108 ends the high-pressure-side abnormality eliminating operation. That is, in the first normal operation, the determination of whether to end the high-pressure-side abnormality eliminating operation is made according to the large/small comparison between Th and Th1.

As described above, in the first normal operation, the controller 108 monitors the temperature Th of the refrigerant flowing through the radiator in the steady operation, and shifts the operating state to the high-pressure-side abnormality eliminating operation if the relationship of Th>Th1 holds. Thereafter, the controller 108 increases gradually the opening degree of the first throttling device and increases gradually the opening degree of the second throttling device until the relationship of Th>Th1 fails to hold.

The control in accordance with the flow chart in FIG. 14 can increase the opening degree of the first throttling device and increase the opening degree of the second throttling device based on the temperature Th of the refrigerant flowing through the radiator. Thereby, it is possible to suppress an excess increase in the temperature Th of the refrigerant flowing through the radiator.

The effect of the control in accordance with the flow chart in FIG. 14 is described with reference to the Mollier diagram in FIG. 15. Before this control is performed, the state of the refrigerant in the refrigeration cycle apparatus 150 changes in the order of O, P, Q, R, S, T, U, V and O in FIG. 15. On the other hand, after this control is performed, the state of the refrigerant in the refrigeration cycle apparatus 150 changes in the order of O′, P, Q, R′, S′, T, U, V′ and O′.

When the pressure of the refrigerant on the high pressure side in the refrigeration cycle is excessively high, it is conceivable to deal with it by increasing only the opening degree of the throttling device on the upstream side of the gas-liquid separator. This can lower the pressure of the refrigerant on the high pressure side. On the other hand, however, this increases the pressure of the refrigerant in the gas-liquid separator. When the pressure of the refrigerant in the gas-liquid separator exceeds the saturation vapor pressure, the liquid refrigerant is injected into the compressor.

In the case where the injection passage 170 is provided with an opening and closing valve as is described in JP 2009-180427 A, for example, it is possible to prevent the liquid refrigerant from being injected into the compressor by closing the opening and closing valve. However, this makes it impossible to obtain the effect of increasing the heating capacity by injection.

In contrast, the control in accordance with the flow chart in FIG. 14 can lower the pressure on the high pressure side in the refrigeration cycle when the pressure on the high pressure side in the refrigeration cycle exceeds the specified value. Furthermore, in the first normal operation, the opening degree of the first throttling device is increased and the opening degree of the second throttling device is increased, thereby it is possible to prevent an increase in the pressure of the refrigerant (State T in FIG. 15) in the gas-liquid separator 104. That is, the control performed in the first normal operation can lower the pressure (temperature, in another word) of the high pressure refrigerant flowing through the radiator to be equal to or lower than the specified value, and keep the pressure of the refrigerant in the gas-liquid separator 104 equal to or lower than the saturation vapor pressure so that the effect of increasing the heating capacity by injection can be obtained.

(Second Normal Operation)

FIG. 16 shows a refrigeration cycle apparatus 250 capable of performing the second normal operation. The refrigeration cycle apparatus 250 is different from the refrigeration cycle apparatus 150 in that the refrigeration cycle apparatus 250 is provided with, instead of the temperature sensor 131, a temperature sensor 132 (high pressure side detector) capable of measuring a temperature Tcom of the refrigerant discharged from the compressor 101. There is no difference other than this, and the action of the refrigeration cycle apparatus 250 in the second normal operation is the same as the action of the refrigeration cycle apparatus 150 in the first normal operation except for the control described below.

Also in the second normal operation, when the pressure of the refrigerant on the high pressure side in the refrigeration cycle becomes excessively high, the high-pressure-side abnormality eliminating operation is performed so that the pressure of the refrigerant flowing into the gas-liquid separator 104 is kept equal to or lower than the saturation vapor pressure while the pressure on the high pressure side in the refrigeration cycle is lowered, as in the first normal operation.

In the high-pressure-side abnormality eliminating operation in the second normal operation, the controller 108 controls the opening degree of the first throttling device and the opening degree of the second throttling device based on the temperature Tcom detected by the temperature sensor 132. Hereinafter, the control (the high-pressure-side abnormality eliminating operation) of the opening degree of the indoor side throttling device 103 (first throttling device) and the opening degree of the outdoor side throttling device 105 (second throttling device) performed by the controller 108 is described with reference to the flow chart shown in FIG. 17.

First, in Step S361, the temperature sensor 132 detects the temperature Tcom of the refrigerant discharged from the compressor 101.

Subsequently, the controller 108 determines the large/small relationship between the temperature Tcom detected in Step 361 and a threshold value Tcom1 (120° C., for example) defined in advance (Step S362). If the relationship of Tcom>Tcom1 holds (YES in Step S362), the sequence proceeds to Step S363 and the controller 108 shifts the operating state from a steady operation to the high-pressure-side abnormality eliminating operation. If the relationship of Tcom>Tcom1 does not hold (NO in Step S362), the sequence returns to Step S361. That is, in the second normal operation, the determination of whether to shift the operating state to the high-pressure-side abnormality eliminating operation is made according to the large/small comparison between Tcom and Tcom1.

In Step S363, the controller 108 increases the opening degree of the first throttling device by ΔA3 and increases the opening degree of the second throttling device by ΔA4, and the sequence proceeds to Step S364. ΔA3 and the ΔA4 are the same as in the first normal operation. In Step S364, the temperature sensor 132 detects once again the temperature Tcom of the refrigerant discharged from the compressor 101. In Step S365, the controller 108 determines the large/small relationship between the temperature Tcom detected in Step 364 and the threshold value Tcom1 defined in advance. If the relationship of Tcom>Tcom1 holds (YES in Step S365), the sequence returns to Step S363 and the controller 108 continues the high-pressure-side abnormality eliminating operation. If the relationship of Tcom>Tcom1 does not hold (NO in Step S365), the sequence returns to Step S361 (the operating state comes back to the steady operation) and the controller 108 ends the high-pressure-side abnormality eliminating operation. That is, in the second normal operation, the determination of whether to end the high-pressure-side abnormality eliminating operation is made according to the large/small comparison between Tcom and Tcom1.

As described above, in the second normal operation, the controller 108 monitors the temperature Tcom of the refrigerant discharged from the compressor 101 in the steady operation, and shifts the operating state to the high-pressure-side abnormality eliminating operation if the relationship of Tcom>Tcom1 holds. Thereafter, the controller 108 increases gradually the opening degree of the first throttling device and increases gradually the opening degree of the second throttling device until the relationship of Tcom>Tcom1 fails to hold.

The control in accordance with the flow chart in FIG. 17 can increase the opening degree of the first throttling device and increase the opening degree of the second throttling device based on the temperature Tcom of the refrigerant discharged from the compressor 101. Thereby, it is possible to lower the temperature Tcom of the refrigerant discharged from the compressor 101 to be equal to or lower than the specified value while keeping the pressure of the refrigerant in the gas-liquid separator 104 equal to or lower than the saturation vapor pressure.

In the first normal operation, the determination of whether to shift the operating state to the high-pressure-side abnormality eliminating operation and the determination of whether to end the high-pressure-side abnormality eliminating operation are made based on the temperature Th of the refrigerant flowing through the radiator. In the second normal operation, these determinations are made based on the temperature Tcom of the refrigerant discharged from the compressor 101. However, the determinations can also be made based on another value. For example, the determinations may also be made based on the temperature of the refrigerant present between the radiator and the first throttling device in the refrigerant circuit 160.

It also is possible to detect, using a pressure sensor instead of the temperature sensor, the pressure of the refrigerant present on the downstream side of the compressor 101 and on the upstream side of the first throttling device in the refrigerant circuit 160 and make the determinations based on this value.

It also is possible to refer to both of the temperature Th of the refrigerant flowing through the radiator and the temperature Tcom of the refrigerant discharged from the compressor 101 by using both of the temperature sensor 131 and the temperature sensor 132. For example, the determination of whether to shift the operating state to the high-pressure-side abnormality eliminating operation and the determination of whether to end the high-pressure-side abnormality eliminating operation may also be made depending on whether one of the relationship of Th>Th1 and the relationship of Tcom>Tcom1 holds. This makes it possible to perform an operation with higher safety than those of the first normal operation and the second normal operation.

In the first normal operation and the second normal operation, the four-way valve (switching device) 120 may be omitted when the refrigeration cycle apparatus 150 and the refrigeration cycle apparatus 250 are used in an application other than air conditioner. This makes the configurations of the refrigeration cycle apparatuses simple, and advantageous from the viewpoints of maintenance and cost.

(Third Normal Operation)

FIG. 18 shows a refrigeration cycle apparatus 350 capable of performing the third normal operation. The refrigeration cycle apparatus 350 is different from the refrigeration cycle apparatus 150 in that the refrigeration cycle apparatus 350 is provided with a temperature sensor 133 (low pressure side detector) capable of measuring the temperature Te of the refrigerant flowing through the outdoor heat exchanger 106 that functions as the evaporator in the heating operation, in addition to the temperature sensor 131 (high pressure side detector) capable of measuring the temperature Th of the refrigerant flowing through the indoor heat exchanger 102 that functions as the radiator in the heating operation. There is no difference other than this, and the action of the refrigeration cycle apparatus 350 in the third normal operation is the same as the action of the refrigeration cycle apparatus 150 in the first normal operation except for the control described below. In the refrigeration cycle apparatus 350 shown in FIG. 18, the indoor side throttling device 103 and the outdoor side throttling device 105 are controlled as described below in the heating operation. By exchanging roles between the temperature sensor 131 and the temperature sensor 133 and roles between the indoor side throttling device 103 and the outdoor side throttling device 105, it is possible to perform the same control as in the third normal operation when the refrigeration cycle apparatus performs the cooling operation.

Also in the third normal operation, when the pressure of the refrigerant on the high pressure side in the refrigeration cycle becomes excessively high, the high-pressure-side abnormality eliminating operation is performed so that the pressure of the refrigerant flowing into the gas-liquid separator 104 is kept equal to or lower than the saturation vapor pressure while the pressure on the high pressure side in the refrigeration cycle is lowered, as in the first normal operation and the second normal operation. In the high-pressure-side abnormality eliminating operation in the third normal operation, the controller 108 controls the opening degree of the indoor side throttling device 103 (first throttling device) and the opening degree of the outdoor side throttling device 105 (second throttling device) based on the temperature Th detected by the temperature sensor 131.

When the pressure (temperature, in another word) of the refrigerant flowing through the evaporator decreases excessively, the performance of the evaporator may not be exhibited sufficiently due to frost formation on the evaporator, etc. Therefore, in the third normal operation, a low-pressure-side abnormality eliminating operation for raising the pressure of the refrigerant flowing through the evaporator is performed when the pressure of the refrigerant flowing through the evaporator is determined to be lower than the specified value even in the case where it is determined not to perform the high-pressure-side abnormality eliminating operation. In the low-pressure-side abnormality eliminating operation in the third normal operation, the controller 108 controls the opening degree of the second throttling device based on the temperature Te detected by the temperature sensor 133.

Hereinafter, the high-pressure-side abnormality eliminating operation and the low-pressure-side abnormality eliminating operation performed by the controller 108 are described with reference to the flow chart shown in FIG. 19. Since the high-pressure-side abnormality eliminating operation in the third normal operation is the same as that in the first normal operation, the steps for performing the operation are indicated with the same reference numerals as those in FIG. 14 and the description thereof is omitted.

If the relationship of Th>Th1 does not hold in Step S262 (NO in Step S262), the sequence proceeds to Step S471.

In Step S471, the temperature sensor 133 detects the temperature Te of the refrigerant flowing through the evaporator.

Subsequently, in Step S472, the controller 108 determines the large/small relationship between the temperature Te and a threshold value Te2 (5° C., for example) defined in advance. If the relationship of Te<Te2 holds (YES in Step S472), the sequence proceeds to Step S473 and the controller 108 shifts the operating state to the low-pressure-side abnormality eliminating operation. If the relationship of Te<Te2 does not hold (NO in Step S472), the sequence returns to Step S261. In this way, in the third normal operation, the determination of whether to shift the operating state to the low-pressure-side abnormality eliminating operation is made according to the large/small comparison between Te and Te2.

In Step S473, the controller 108 increases the opening degree of the second throttling device by ΔA5 and the sequence proceeds to Step S474. Here, ΔA5 can be an arbitrary value. In Step S474, the temperature sensor 133 detects once again the temperature Te of the refrigerant flowing through the evaporator. In Step S475, the controller 108 determines the large/small relationship between the temperature Te detected in Step S474 and the threshold value Te2 defined in advance. If the relationship of Te<Te2 holds (YES in Step S475), the sequence returns to Step S473 and the controller 108 continues the low-pressure-side abnormality eliminating operation. If the relationship of Te<Te2 does not hold (NO in Step S475), the sequence returns to Step S261 (the operating state comes back to the steady operation) and the controller 108 ends the low-pressure-side abnormality eliminating operation. That is, in the third normal operation, the determination of whether to end the low-pressure-side abnormality eliminating operation is made according to the large/small comparison between Te and Te2.

In the control in accordance with the flow chart in FIG. 19, the low-pressure-side abnormality eliminating operation can suppress an excess decrease in the temperature Te of the refrigerant flowing through the evaporator even in the case where it is determined not to perform the high-pressure-side abnormality eliminating operation.

In the third normal operation, the determinations of whether to shift the operating state to the high-pressure-side abnormality eliminating operation and whether to end the high-pressure-side abnormality eliminating operation are made based on the temperature Th of the refrigerant flowing through the radiator. However, the determinations may be made based on the temperature of the refrigerant discharged from the compressor 101, as in the second normal operation.

Moreover, although the determination of whether to perform the low-pressure-side abnormality eliminating operation is made based on the temperature Te of the refrigerant flowing through the evaporator in the third normal operation, it can be made based on another value. For example, it is possible to measure the temperature of the refrigerant drawn into the compressor 101 by the temperature sensor and compare the detected temperature with another threshold value so as to make the determination based on this. That is, the temperature sensor may be provided at any position as long as it is on the downstream side of the second throttling device and on the upstream side of the compressor 101, where the refrigerant has a low pressure.

It also is possible to detect, using a pressure sensor instead of the temperature sensor, the pressure of the refrigerant present on the downstream side of the second throttling device and on the upstream side of the compressor 101 in the refrigerant circuit 160 so as to determine whether to perform the low-pressure-side abnormality eliminating operation based on this value.

(Fourth Normal Operation)

FIG. 20 shows a refrigeration cycle apparatus 450 capable of performing the fourth normal operation. The refrigeration cycle apparatus 450 is different from the refrigeration cycle apparatus 150 in that the refrigeration cycle apparatus 450 is provided with a pressure sensor 140 (intermediate pressure side pressure sensor) for measuring the pressure of the refrigerant in the gas-liquid separator 104 and a temperature sensor 134 (radiator outlet temperature sensor) for detecting the temperature of the refrigerant flowing out of the indoor heat exchanger 102, in addition to the temperature sensor 131 capable of measuring the temperature Th of the refrigerant flowing through the indoor heat exchanger 102 that functions as the radiator in the heating operation. There is no difference other than this, and the action of the refrigeration cycle apparatus 450 in the fourth normal operation is the same as the action of the refrigeration cycle apparatus 150 in the first normal operation except for the control described below. In the refrigeration cycle apparatus 450 shown in FIG. 20, the indoor side throttling device 103 and the outdoor side throttling device 105 are controlled as described below in the heating operation. By providing the temperature sensor 131 to the outdoor heat exchanger 106 and providing the temperature sensor 134 between the outdoor side throttling device 105 and the outdoor heat exchanger 106, and exchanging roles between the indoor side throttling device 103 and the outdoor side throttling device 105, it is possible to perform the same control as in the fourth normal operation when the refrigeration cycle apparatus performs the cooling operation.

Also in the fourth normal operation, when the pressure of the refrigerant on the high pressure side in the refrigeration cycle becomes excessively high, the high-pressure-side abnormality eliminating operation is performed so that the pressure of the refrigerant flowing into the gas-liquid separator 104 is kept equal to or lower than the saturation vapor pressure while the pressure on the high pressure side in the refrigeration cycle is lowered, as in the first normal operation, the second normal operation, and the third normal operation. In the high-pressure-side abnormality eliminating operation in the fourth normal operation, the controller 108 controls the opening degree of the first throttling device and the opening degree of the second throttling device based on the temperature Th detected by the temperature sensor 131, a temperature Tec detected by the temperature sensor 134, and a pressure Pi detected by the pressure sensor 140.

Hereinafter, the control (high-pressure-side abnormality eliminating operation) of the opening degree of the indoor side throttling device 103 (first throttling device) and the opening degree of the outdoor side throttling device 105 (second throttling device) performed by the controller 108 is described with reference to the flow chart shown in FIG. 21.

The flow chart shown in FIG. 21 is given by adding Step S564 to Step S568 between Step S263 and Step S264 in the flow chart shown in FIG. 14. Hereinafter, the difference from the flow chart of FIG. 14 is described.

In the fourth normal operation, the controller 108 increases the opening degree of the first throttling device by ΔA3 and increases the opening degree of the second throttling device by ΔA4 in Step S263, and the sequence proceeds to Step S564. In the fourth normal operation, the values of ΔA3 and ΔA4 can be arbitrary values.

The temperature sensor 134 detects the temperature Tec of the refrigerant flowing out of the radiator in Step S564, and the sequence proceeds to Step S565.

In Step S565, the controller 108 determines a saturation vapor pressure Pi6 based on the temperature Th detected in Step S261 and the temperature Tec detected in Step S564. A table or the like can be used when determining the saturation vapor pressure Pi6.

Subsequently, in Step S566, the pressure sensor 140 detects the pressure Pi of the refrigerant in the gas-liquid separator 104 and the sequence proceeds to Step S567.

In Step S567, the controller 108 determines the large/small relationship between the pressure Pi and the saturation vapor pressure Pi6. If the relationship of Pi>Pi6 holds (YES in Step S567), the sequence proceeds to Step S568 and the controller 108 decreases the opening degree of the first throttling device by ΔA6 and increase the opening degree of the second throttling device by ΔA7, and the sequence proceeds to Step S264. If the relationship of Pi>Pi6 does not hold (NO in Step S567), the sequence proceeds to Step S264. Since ΔA6 is smaller than ΔA3, the pressure of the refrigerant flowing through the radiator (that is, the pressure on the high pressure side) is lowered even in the case where both controls of Step S263 and Step S568 are performed.

The control in accordance with the flow chart in FIG. 21 can lower the pressure of the high pressure refrigerant flowing through the radiator to be equal to or lower than the specified value.

Furthermore, the control in accordance with the flow chart in FIG. 21 can monitor the pressure of the refrigerant in the gas-liquid separator 104 and lower it as needed. Thereby, it is possible to set the pressure of the refrigerant in the gas-liquid separator 104 to be equal to or lower than the saturation vapor pressure more reliably when the refrigeration cycle apparatus performs the fourth normal operation than when the refrigeration cycle apparatus performs the first normal operation, the second normal operation, and the third normal operation.

Moreover, in the first normal operation, the second normal operation, and the third normal operation, it is necessary to set the pressure of the refrigerant flowing into the gas-liquid separator 104 to be equal to or lower than the saturation vapor pressure in a reliable manner only by Step S263 (or by Step S363). Therefore, it is preferable to set the amount of change ΔA4 in the opening degree of the second throttling device to be somewhat larger than an amount of change ΔA4 determined by experiment, etc. That is, the pressure of the refrigerant flowing into the gas-liquid separator 104 may be lower than needed. In contrast, in the fourth normal operation, it is possible to keep reliably the pressure of the refrigerant flowing into the gas-liquid separator 104 equal to or lower than the saturation vapor pressure by Step S564 to Step S568. Therefore, the amount of change ΔA4 in Step S263 can be smaller in the fourth normal operation than that in the first normal operation, the second normal operation, and the third normal operation. This makes it possible to control the opening degree of the second throttling device so that the pressure of the refrigerant flowing into the gas-liquid separator 104 is equal to or lower than the saturation vapor pressure and close to the saturation vapor pressure. As a result, the refrigeration cycle apparatus can be operated more effectively.

Instead of detecting the temperature Th of the refrigerant flowing through the radiator by the temperature sensor 131, it is possible to detect the pressure of the refrigerant present on the downstream side of the compressor 101 and on the upstream side of the first throttling device in the refrigerant circuit 160 so as to determine whether to shift the operating state to the high-pressure-side abnormality eliminating operation and whether to end the high-pressure-side abnormality eliminating operation based on this value. Thereby, the saturation vapor pressure can be determined also from this value and the temperature Tec.

In the fourth normal operation, the pressure sensor 140 provided in the gas-liquid separator 104 detects directly the pressure Pi of the refrigerant in the gas-liquid separator 104, but the pressure Pi does not necessarily have to be detected directly. For example, the pressure Pi of the refrigerant in the gas-liquid separator 104 may be determined indirectly from the pressure or temperature of the refrigerant present between the first throttling device and the gas-liquid separators 104 or between the gas-liquid separator 104 and the second throttling device in the refrigerant circuit 160, or from the pressure or temperature of the refrigerant in the injection passage 170.

Moreover, although the saturation vapor pressure Pi6 is determined from the detected temperature Th and temperature Tec in the fourth normal operation, a value in accordance with the value detected by the temperature sensor 131 may be used as the saturation vapor pressure Pi6, for example. This simplifies the control performed by the controller 108, making it possible to obtain a useful configuration from the view point of computer resource.

The first normal operation to the fourth normal operation described above can be summarized as follows.

That is, it is preferable that the refrigeration cycle apparatus capable of performing the normal operation include: the refrigerant circuit including the compressor for compressing the refrigerant, the radiator that allows the refrigerant compressed in the compressor to radiate heat, the first throttling device for expanding the refrigerant that has radiated heat in the radiator, the gas-liquid separator for separating the refrigerant expanded in the first throttling device into the gas phase refrigerant and the liquid phase refrigerant, the second throttling device for expanding the liquid phase refrigerant separated out in the gas-liquid separator, and the evaporator for evaporating the refrigerant expanded in the second throttling device; the injection passage through which the gas phase refrigerant separated out in the gas-liquid separator is supplied to the compressor during the compression process; a high pressure side detector for detecting the temperature or the pressure of the refrigerant present on the downstream side of the compressor and on the upstream side of the first throttling device in the refrigerant circuit; and the controller for performing the high-pressure-side abnormality eliminating operation in which when the value detected by the high pressure side detector exceeds the specified value, the controller increases the opening degree of the first throttling device and increases the opening degree of the second throttling device so as to lower the high pressure of the refrigeration cycle while keeping the pressure of the refrigerant in the gas-liquid separator equal to or lower than the saturation vapor pressure.

This configuration makes it possible to increase the opening degree of the first throttling device to lower the pressure of the refrigerant on the high pressure side in the refrigeration cycle when the pressure of the refrigerant on the high pressure side in the refrigeration cycle is excessively high. Furthermore, in the above-mentioned refrigeration cycle apparatus, not only the opening degree of the first throttling device but also the opening degree of the second throttling device is increased. When the opening degree of the second throttling device is increased, the pressure of the refrigerant in the gas-liquid separator is lowered. That is, by increasing the opening degree of the first throttling device as well as the opening degree of the second throttling device, it is possible to suppress an increase in the pressure of the refrigerant in the gas-liquid separator while lowering the pressure of the refrigerant on the high pressure side in the refrigeration cycle, so that the pressure of the refrigerant in the gas-liquid separator is kept equal to or lower than the saturation vapor pressure. Accordingly, it is possible to suppress an abnormal increase in the pressure on the high pressure side in the refrigeration cycle, and to inject the refrigerant into the compressor while preventing the liquid refrigerant from being injected into the compressor.

Preferably, the above-mentioned refrigeration cycle apparatus further includes the low pressure side detector for detecting the temperature or the pressure of the refrigerant present on the downstream side of the second throttling device and on the upstream side of the compressor in the refrigerant circuit, and if the value detected by the low pressure side detector is smaller than the specified value, the controller performs the low-pressure-side abnormality eliminating operation for increasing gradually the opening degree of the second throttling device even in the case where it does not perform the high-pressure-side abnormality eliminating operation.

Preferably, in the above-mentioned refrigeration cycle apparatus, the controller repeats, in the high-pressure-side abnormality eliminating operation, the main step of increasing the opening degree of the first throttling device by the specified amount of ΔA3 and increasing the opening degree of the second throttling device by the specified amount of ΔA4 until the value detected by the high pressure side detector falls below the specified value.

In the above-mentioned refrigeration cycle apparatus, it is preferable that the high pressure side detector is a radiator temperature sensor for detecting the temperature of the refrigerant flowing through the radiator. Preferably, the above-mentioned refrigeration cycle apparatus further includes the pressure sensor for detecting the pressure of the refrigerant in the gas-liquid separator, and the radiator outlet temperature sensor for detecting the temperature of the refrigerant flowing out of the radiator. Preferably, the controller calculates the saturation vapor pressure of the refrigerant flowing into the gas-liquid separator from the values detected by the radiator temperature sensor and the radiator outlet temperature sensor and determines whether the pressure detected by the pressure sensor exceeds the saturation vapor pressure every time when performing the main step, and when the pressure detected by the pressure sensor exceeds the saturation vapor pressure, the controller decreases the opening degree of the first throttling device by a value smaller than ΔA3 and increases further the opening degree of the second throttling device.

INDUSTRIAL APPLICABILITY

The refrigeration cycle apparatus according to the present invention can be utilized as a refrigeration cycle apparatus for various applications, such as hot water supply and air conditioning. 

1. A refrigeration cycle apparatus comprising: a refrigerant circuit including a compressor for compressing a refrigerant, a condenser for condensing the refrigerant compressed in the compressor, a first throttling device for expanding the refrigerant condensed in the condenser, a gas-liquid separator for separating the refrigerant expanded in the first throttling device into a gas phase refrigerant and a liquid phase refrigerant, a second throttling device for expanding the liquid phase refrigerant separated out in the gas-liquid separator, and an evaporator for evaporating the refrigerant expanded in the second throttling device, the refrigerant circuit being a refrigerant circuit through which the refrigerant that does not reach a supercritical state after being compressed in the compressor circulates; an injection passage through which the gas phase refrigerant separated out in the gas-liquid separator is supplied to the compressor during a compression process; a detector for detecting a temperature or a pressure of the refrigerant present on a downstream side of the first throttling device and on an upstream side of the second throttling device in the refrigerant circuit or present in the injection passage; and a controller for decreasing an opening degree of the first throttling device when the controller recognizes, by the detector, that a pressure of the refrigerant flowing into the gas-liquid separator exceeds a specified pressure lower than a saturation vapor pressure, in a starting operation, a defrosting operation or a stopping operation.
 2. The refrigeration cycle apparatus according to claim 1, wherein the controller decreases the opening degree of the first throttling device and increases an opening degree of the second throttling device when the controller recognizes, by the detector, that the pressure of the refrigerant flowing into the gas-liquid separator exceeds the specified pressure in the starting operation, the defrosting operation or the stopping operation.
 3. The refrigeration cycle apparatus according to claim 1, wherein the detector is a temperature sensor, and in the starting operation, the defrosting operation or the stopping operation, the controller compares a temperature Ti detected by the temperature sensor to a threshold value Ti1, and determines that the pressure of the refrigerant flowing into the gas-liquid separator exceeds the specified pressure if a relationship of Ti>Ti1 holds.
 4. The refrigeration cycle apparatus according to claim 1, wherein at least in the starting operation, the controller decreases the opening degree of the first throttling device, or decreases the opening degree of the first throttling device and increases an opening degree of the second throttling device when the controller recognizes, by the detector, that the pressure of the refrigerant flowing into the gas-liquid separator exceeds the specified pressure.
 5. The refrigeration cycle apparatus according to claim 4, wherein the controller ends the starting operation after a specified period of time has elapsed since start of the operation.
 6. The refrigeration cycle apparatus according to claim 4, further comprising a condenser temperature sensor for detecting a temperature of the refrigerant flowing through the condenser, wherein the controller compares a rate of change with time, ΔTc, calculated from the temperature detected by the condenser temperature sensor to a threshold value ΔTc1, and ends the starting operation if a relationship of ΔTc>ΔTc1 holds.
 7. The refrigeration cycle apparatus according to claim 4, further comprising an evaporator temperature sensor for detecting a temperature of the refrigerant flowing through the evaporator, wherein the controller compares a rate of change with time, ΔTe, calculated from the temperature detected by the evaporator temperature sensor to a threshold value ΔTe1, and ends the starting operation if a relationship of ΔTe>ΔTe1 holds.
 8. The refrigeration cycle apparatus according to claim 1, further comprising a switching device capable of switching between a heating operation and a cooling operation. 